On the Trail of the Cat, Scientists Find Surprises

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On the Trail of the Cat, Scientists Find Surprises

By Rob Stein

Washington Post Staff WriterMonday, March 17, 2008; Page A10

If cat owners know anything about their pets, it’s how enigmatic the creaturescan be. But scientists have begun to pull back the feline veil, using the latestmolecular tools to get a peek at their origins.

Tracing Kitty’s Genes

“Cats are certainly more mysterious and complex than we would ever think,” saidLeslie A. Lyons, who studies cat genetics at the School of Veterinary Medicineat the University of California at Davis. “However, we’re starting to get theirstory.”

In one of the most comprehensive explorations of cats’ origins to date, Lyonsand her colleagues spent about five years collecting feline DNA, poking behindthe whiskers of more than 1,100 Persians, Siamese, street cats and householdtabbies around the world to swab inside their mouths. The genetic samples camefrom 22 breeds of fancy cats, mostly in the United States, along with anassortment of feral and pet cats in Korea, China, Kenya, Israel, Turkey,Vietnam, Singapore, Sri Lanka, Tunisia, Egypt, Italy, Finland, Germany, theUnited States and Brazil.

By analyzing 39 genetic signposts in the samples, the researchers were able toinvestigate a variety of questions, including which breeds are most closelyrelated and where they most likely originated.

The first thing the group did was confirm a report published last June in thejournal Science that the domestication of cats about 10,000 years ago appearedto have occurred in an area known as the Fertile Crescent, which stretches fromTurkey to northern Africa and to modern-day Iraq and Iran.

“Our data support the Fertile Crescent, specifically Turkey, as one of theorigin sites for cats,” said Lyons, who published her findings in the Januaryissue of the journal Genomics. “Turkey was part of the Fertile Crescent andhence was one of the earliest areas for agricultural development.”

Cats probably started living close to humans when people evolved from nomadicherding to raising livestock and crops and started storing food, which attractedmice and other rodents. Cats found good hunting there, and humans surelyappreciated the sly little predators’ help protecting their stocks.

“There was a mutual benefit,” Lyons said. “There was a food source of mice andrats all around the grain. So it was beneficial for both cats and humans as thecats came closer to human populations and kind of domesticated themselves.”

From there, domesticated cats started to radiate out to different parts of theworld, often following humans on their migrations. Today cats can be dividedgenetically into four broad groups: those from Europe, the Mediterranean, EastAfrica and Asia.

But Lyons and her colleagues also made surprising discoveries about individualbreeds. “We wanted to see whether breeds actually came from what was thought tobe their geographical origins,” Lyons said.

The Japanese bobtail, for example, does not seem genetically similar to catsfrom Japan, indicating the breed may have originated elsewhere. “Either itdidn’t originate in Japan or there’s been so much Western influence that theyhave lost their initial genetic signal,” Lyons said.

Despite its name, the Persian, the oldest recognized breed, looks as though itactually arose in Western Europe and not Persia, which today is Iran.“If it came from Iran, you would think it would look like cats from Turkey andIsrael,” she said. Instead, the Persian “looked more like a Western Europeancat.”

When the researchers examined the genes of what are thought to be distinctbreeds, they were unable to find significant differences among many of them.

“An example would be Persian and exotic shorthairs. When you look at those twobreeds, you can’t distinguish them from one another” by their genes, she said.

The same was true for the Burmese and the Singapura, as well as the Siamese andthe Havana brown. While Havana browns are considered a separate breed in theUnited States, European cat breed associations consider them a color variationof Siamese.

“Some people will say, ‘Ha, ha. I told you so.’ Some other people will bedisappointed,” Lyons said.

Breeds look very different because of variations in a single gene, which is notenough to distinguish them genetically, she said.

The researchers also found interesting relationships that track human history.Italian and Tunisian cats, for example, are a mix of Western European andMediterranean cats, probably reflecting the close historical ties betweenTunisia and western Europe. Cats from Sri Lanka and Singapore are a geneticmelange of cats from Southeast Asia, Europe and elsewhere, which could be a“relic of British colonialism,” the researchers wrote. The same goes for theAbyssinian.

The finding that cat lovers should be concerned about is that some breeds havebecome so inbred that the amount of genetic variation among them is gettingdangerously low. That tends to lead to higher levels of illness, Lyons said.

“That could have consequences for the cats’ health. The more genetic variation,generally the healthier the population will be. So some cat breeders need to becareful that there’s not too much inbreeding going on,” she said.

The Burmese and Singapura breeds had the least diversity, she said, whileSiberians had the greatest, along with Norwegian forest cats, Maine coons andJapanese bobtails.

About half the breeds examined had genetic variation comparable to randomly bredcats, which is good, but the other half had less.

“You don’t want to say they are in trouble, but it’s something we should note,”Lyons said.

The findings could help guide breeders, Lyons and others said.

“This is new and very useful information,” said Susan Little, president of theWinn Feline Foundation, a nonprofit group that partially funded the work. “Ithelps improve the ability of breeders to reduce the prevalence of disease bydeveloping a healthy breeding program. It’s extremely important.”

Despite the shrinking genetic diversity, purebred cats remain far moregenetically diverse than purebred dogs, noted Marilyn Menotti-Raymond, whostudies cat genetics at the National Cancer Institute. That’s because peoplehave been breeding cats for about 200 years at most, and there is moreinterbreeding than among purebred dogs, she said.

“Everyone is aware of the problems that can occur from the small gene pool insome dog breeds,” said Menotti-Raymond, who, in the same issue of the journalGenomics, reported similar findings in a different sample of 611 catsrepresenting 38 breeds. “I was actually surprised at the level of geneticdiversity in cats, and that’s good.”

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